The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. For example, lactate, cholesterol, and bilirubin should be monitored in certain individuals. In particular, determining glucose in body fluids is important to diabetic individuals who must frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests may be used to determine what, if any, insulin or other medication needs to be administered. In one type of testing system, test sensors are used to test a fluid such as a sample of blood.
According to some existing techniques, a lancet may be used to pierce a user's skin to draw fluid (e.g., blood) from the user. This fluid is then used with an instrument or meter to determine an analyte (e.g., glucose) concentration. Piercing a user's skin each time an analyte concentration reading is desired is an inconvenient and invasive procedure. Moreover, the procedure is undesirable because of the resulting pain and discomfort often experienced by a user.
One non-invasive method for obtaining a sample for determining an analyte concentration involves using a transdermal sample of one or more analytes found in, for example, interstitial fluid (ISF). In this method, a transdermal test sensor is placed on a user's skin. The transdermal sensor typically includes a hydrogel composition to facilitate the extraction of the analyte of interest from the ISF via the user's skin to an analyte-testing instrument or meter. The hydrogel must be sufficiently mechanically and thermally stable to provide a relatively static, reactive, and aqueous conduct between a dermal sampling site and an analyte-testing instrument.
One problem with existing transdermal test sensors relates to having a hydrogel that is sufficiently hydrated and can maintain such hydration. Inadequate hydration may be caused by exposure to the outside environment and/or the lack of a hermetic seal between the skin and the test sensor. The level of hydration of the hydrogel (e.g., solvent content) generally decreases over time. If the level of hydration of the hydrogel falls below a certain level, the hydrogel may cease to provide intimate contact between the skin and the hydrogel and/or the hydrogel and the test sensor. Such intimate contact is necessary for accurate testing results.
Thus, it would be desirable to have a transdermal test sensor that assists in addressing one or more of the above disadvantages.